Radio receiving system



Feb. 2, 1932. v F. A. KoLs'rER RADIO RECEIVING SYSTEM Filed Oct. 2, 1925 W/T/vf'lss.

Patented Feb. 2, -19322 untreu @STATES PATENT OFFICE FREDERICK A. KOLSTER, OE SAN J' OSE, CALIFORNIA, 'ASSIG-NOR TO TELEGRAPH COMPANY, OF SAN FRANCISCO, CALIFORNIA, A.' CORPORATION 0F CALIFORNIA Immo RECEIVING SYSTEM Application led October 2, 1923. Serial No. 666,060.

This invention relates to a system for receiving radio frequency electrical energy, and

more particularly to a scheine whereby they desired signals-may be selected from other interfering signals, and amplified. This I accomplish by the aid of a selector, which is arranged with respect to the system to provide a path of relatively low impedance for the `interfering signals. The amplifiers being in a separate path are to a great extent left unaected by the interfering signals.

Such an arrangement of circuits has been 25 maximum amplifying power.`

My invention possesses other advantageous. features, some of which with the foregoing, will be set forth at length in the following description, where I shall outline in full that form of thel invention which I have selected for illustration in the drawing accompany' ing and forming part of the ,present specification. Although I have shown in the draw# inglbut one embodiment of my invention, I

35 do not desire to be limited thereto, since thel invention as expressed in the claims may be *embodied in other forms also.

' Referring to the drawing;

r The single figure is a wiring diagram of a 40 `radio receiving system embodying my invention. i

' In the present instance I have illustrated my invention as applied to a radio receiving -system usinga pluralitypof stages .of radio frequency amplifiers 1, 2, and 3 of the electron emission type. However, it is evident that the principles disclosed may be readily applied to audio frequency amplifiers orto a combination of audio and .radio frequency amplifiers; although the invention is perhaps most advantageously utilized in connection with radio frequency amplification.

The oscillations to be amplified are in this instance absorbed `from an energy transmiting medium in a circuit such as the antenna '4, loading coil 5, variable condenser 6, and a ground connection 7 The first stage of amplification through the three-electrode device 1 is secured by coupling the filament-grid circuit to the antenna circuit, as for example, by the aid of coil 8 inductively associated with the antenna coil 5. the `maximum effect, a tuning condenser 9 is bridged across the coil 8, the terminals of which are respectively connected to the grid 10 and an electron emitting element 11 of the amplifier 1. and the element 11 is the input circuit for the amplifier, the operation being dependent upon the variations. in accordance with the signal amplified, in the electromotive force betweenthesetwoelements. These variations are amplified i the output circuit for the amplifier 1, which circuit includes a cold electrode or plate 12, enclosed within the amplifier tube, an impedance device 13, aplate battery 14, and the element l1. Since such amplifying devices are well known, it is not at all necessary to enter into further detail as regards the theory of operation. It may be mentioned however that the electron emitting element 11 is usually in the form of a filament which is heated to a temperature sufficient to cause lit to emit electrons. For producing lthe heating effect, a source of' electrical energy, such as the battery 15, may be utilized.

The amplified signals through the transl' lating device 13 are passed through a second 'amplifier stage; forthis purpose the second thermionic "amplifier 2 maybe used. This amplifierloperates in substantially. the same manner as the amplifier 1. It *fs however 'fne'cessarylto' couple the two tubes 1 and 2,

and my invention is most concerned iny the manner ingtwhichjthis is accomplished. It hasbeen shown that in order 'to secure a'high degree of amplification, the output circuit forthe tube should have an impedance or a resistancecomparable withthat of the tube itseli, furthermore, the coupling between In order to secure The circuit between the grid 1() '13 ties.

this circuit and the input circuit of the succeeding tube should be as close as possible, so as to utilize the energy in this output circuit to the maximum extent. Tn order to fulfill these conditions, the device 13 in th-e output circuit of amplifier. 1 is shown as having a yvery large impedance, which may be either a very large resistance or a very large inductance, or a combination of these two quanti- Furthermore, the amplifier 2 is directively cou led to the output circuit of amplifier l, pre erably by means of the lead 16 and the stopping condenser 19 connecting the plate terminal of the high impedance 13 to the grid 17 of the amplifier 2. The lament 18 for this amplifier is shown as connected to the heating battery 15. The battery connections also serve as a direct coupling between the two amplifiers 1 and 2. The stopping condenser 19 is inserted in lead 16 to prevent the high potential of the plate battery'14 from being impressed upon the grid Although the mode of coupling just` described has been proposed heretofore, it has l are not attainable for short wave operation.

My invention aims to over-come this defect, by connecting a selector such as 20 across the grid-17 andfilament 18 of the coupled tube. This selector includes referably an nductance coil 21 and a varia le condenser 22 in parallel. The condenser 22 isa'd] usted tosuch a pointV that the selector circuit between th-e grid and filament has substantially infinite impedance for energy of the selected frequency which it is desired to amplify. Thus no substantial lamount of s ignaling energy can fiow in this circuit, which then has a very high impedance to currents ator near the frequency of the radio Signals which are to be amplified. To secure this result, either the condenser 22 or the inductance 21 is adjusted so that at this frequency the inductive reactance of coil 21 is equal to the capacitive reactance of condenser 22.

Under such circumstances Whatever current `of the tuned frequency may be flowing in the .coil 21 has itsexact counterpart in the cur- Irent flowing in condenser 22, since these elements have the same electromotlve force 11npressed across them. .Thus so far as the ezxternal circuit is cncerned,r these two currents cancel each other, and none can flow through ythe selector, although there may be a :circulatory current -i-n the closed path form-ed by the elements '2 1 and 22.

The operation of the selector to by-pass Lacasse interfering signaling energy has been de tailed at length in the application heretofore identified. llt is accordingly unnecessary to discuss this operation here. Its new function in thecombination disclosed l believe is to alter the influence of the capacity between the electrodes of the tubes, whereby the dethigh resistance 23 may be utilized, which.

provides substantially similar effects. A wave selector 24 is again used between the grid and filament of tube 3 for the same purpose as described heretofore. As many stages of radio frequency amplification may be further added as desired, utilizing the coupling system constituted by non-inductive high resistance 35 and selector circuit 33. lft is however considered unnecessary to disclose .these further stages, since obviously they may be added to the system in accordance with the teachings already outlined. The devices 13, 23 and 35 each'constitute an untuned element having a high radio frequency impedance and may -be formed by any equivalent element which possesses a high radio frequency impedance characteristic.

, `Tn order to detect the signals, there may be provided a three-electrode thermionic device 25, having a heated filament 26, grid 27, and plate 28. The grid 27 is connected to the output circuit of amplifier 3 through the usual,

grid condenser 29 and grid leak 30. The filament 26 may also beconnected in any appropriate manner with the amplifier circuit. The output circuit of .detector includes the plate 28, a translating device such as phones 31, and a battery 32. A selector 33 may also -be connected across the grid 27 and filament 26 of the detector 25, so as to shunt Whatever interfering energy there may be present in the output of amplifier 3. The coupling between the output circuit of tube 3 and the detector tube 25 is effected by the non-inductive high resistance 35 similar to' the non-inductive resistance 23 between the tubes 2 and 3. As indicated byI the dotted lines. '34 and the legend, all of the selectors 20, 24 and 33 maybe arranged to have a. common control, so that they may be simultaneously adjusted by a single operation. This feature is of importance, since thereby thel adjustments may be very quickly made.

Itis of course possible to provide audiol frequency amplifiers with this circuit. Since the application of these amplifiers presents control whereby the system may be tuned for y les no essentially new features they have been l ing a variable condenser for selectively tunomitted.

It is evident that from the foregoing disclosure the advantages of close coupling between the tubes by the aid of a high impedancev in the output circuits may be obtained for short wave operation when use is made of my invention.

I claim:

1. A cascade radio frequency amplifier adapted to selectively amplify energy over a substantial range of radio frequencies comprising at least two electron emission tubes each having input and output circuits, an untuned element having a high radio frequency impedance coupling together the output of the first tube with the input of the second and having a high impedance throughout said range of frequencies, a similar high radio frequency impedance coupling together the output of the second tube with the input of a translating circuit, a variable selector connected in parallel with the input of the second tube, and a similar selector in parallel with the input of each electron tube circuit, each selector comprising an inductance element and a condenser element in parallel with the inductance'element of each selector, one of said elements being simultaneously variable by operation 'of a single any one frequency within said range.

2. A cascade radio frequency amplifier adapted to selectively amplify energy over a substantial range of radio frequencies comprising at least two electron emissiontubes each having input and output circuits, an untuned element having a high radio frequency impedance over said range of radio ing the input of the second tube, means including a second variable condenser for selectively tuning the input of the translating circuit, independent inductances connected in shunt with each of said variable condensers, a common control for varying said condensers in unison, and means including an 'independently variable condenser for selectively coupling the input of the first tube to asource of radio frequency energy.

In testimony whereof, I have hereunto set my hand.

FREDERICK A. KOLSTER.

requencies for coupling together the output u of the first tube w-ith the input of the second tube, a similar high impedance coupling together the output of the second tube with a translating circuit, a variable selector con-y nected in parallel with theinput of the second tube, asimilar selector connected in par allel with the input of said translating circuit, each selector comprisin a variable condenser in parallel with a xed inductance, and a single control for varying the respective capacitances lof said condensers in unison, whereby the s stem may be varied to amplify any selected fiiequency within said range.

3. A radio receiving system adapted to selectively receive energy over a substantial range of radio frequencies comprising at least two .electron emission amplifying tubes each having input and output circuits, an untuned element having a high radio frequency im# pedance for coupling the output of the first tube to the input of the second tube, an independent radio frequency impedance for coupling the output of the second tube to the input of a translating circuit, means includ` 

